A photographic material generally has an electric insulating support and a photographic layer, and therefore, an electric charge is often accumulated on the material during manufacture or use thereof because of contact, friction or peeling with the surface of the same or different substance. The accumulated static charge causes various problems, the most significant of which is that the light-sensitive emulsion layer in the material is sensitized by discharge of the static charge accumulated before development, to cause spots or branched or feather-like streaks on the photographic film developed. These are called "static marks", which lower the commercial value of photographic films if they do not ruin them. For example, if such static marks occur in medical or industrial X-ray films, etc., it is easily recognized that these would result in an extremely dangerous judgment. The phenomenon of static marks appears only after development of films and is therefore an extremely troublesome problem. In addition, the accumulated static charge would cause secondary disadvantages, for example, including adhesion of dust on the surface of the film or difficulty of uniform coating thereon.
Such static charge is often accumulated during manufacture and use of photographic materials, as mentioned above. In particular, this is caused by contact and friction between photographic film and rollers during manufacture of films, or by separation of the emulsion surface from the support surface during reeling up or reeling back of films. In the case of finished products, the static charge often occurs by separation of the emulsion surface from the support surface during reeling-up and exchange of photographic films. This would also occur because of contact of X-ray films with machine parts or fluorescent sensitized paper in automatic photographing machines and the successive separation of the films from the parts or paper in the machine. The static marks of photographic materials caused by the accumulation of such static charge become more remarkable with elevation of the sensitivity of the photographic materials as well as with acceleration of the processing speed. In particular, photographic materials recently have been subjected to severe conditions in many cases, for example., for extreme elevation of the sensitivity of the materials and for rapid coating, rapid photographing and rapid automatic development of the materials, and therefore, the materials are increasingly damaged by static marks.
In order to eliminate the difficulties of static charge mentioned above, it is preferred to add an antistatic agent to photographic materials. However, the antistatic agents generally used in other technical fields cannot always be used for photographic materials, since the antistatic agents which can be used for photographic materials are restricted by various conditions which are specific to photographic materials. Specifically, the antistatic agents which can be used for photographic materials are required to satisfy various conditions, in addition to excellent antistatic properties: they must not have any bad influences on photographic characteristics, such as sensitivity, fog property, graininess, sharpness, etc.; they must not have any bad influences on the film strength of photographic materials (that is, the photographic materials must not become easily damaged by friction or scratches because of the addition of the antistatic agents); they must not have any bad influences on the blocking-resistance of photographic materials (that is, the surface of the photographic material must not become easily adherable to the surface of other photographic materials or other substances because of the addition of the antistatic agents); they must have not cause the acceleration of fatigue of processing solutions for photographic materials, stain conveyer rollers, lower the adhesion strength between the constituting layers of photographic materials, etc. Accordingly, the application of antistatic agents to photographic materials is restricted by various conditions.
One method for eliminating static charge difficulties is to elevate the electroconductivity on the surface of photographic materials so that the static charge may rapidly be diffused away in a short period of time prior to discharge of the accumulated charge.
Accordingly, various methods for improving the electroconductivity of the support and the coated layers of photographic materials have been investigated and utilization of various hydroscopic substances, water-soluble inorganic salts, certain kinds of surfactants, polymers, etc. has been tried.
Among them, surfactants are important in view of their antistatic capacity, and for example, there are known anion, betaine and cation surfactants described in U.S. Pat. No. 3,082,123, 3,201,251, 3,519,561, 3,625,695, West German Patent Nos. 1,552,408, 1,597,472, Japanese Patent Application (OPI) Nos. 85826/64, 129623/78, 159223/79, 197213/73 (the term "OPI" as used herein means a "published unexamined Japanese patent application"), Japanese Patent Publication Nos. 39312/71, 11567/74, 46755/76, 15517/80, as well as nonionic surfactants described in Japanese Patent Publication No. 17882/73, Japanese Patent Application (OPI) No. 80023/77, West German Patent Nos. 1,422,809, 1,422,818, Australian Patent No. 54441/1959.
However, these substances are specific to film supports and photographic compositions, and therefore, some are effective only for specific film supports and specific photographic light-sensitive emulsions and photographic constitutional elements, but cannot be used for other film supports and photographic constitutional elements as an antistatic agent, as described in, for example, Japanese Patent Publication No. 17882/73 which corresponds to U.S. Pat. No. 3,415,649. Also, some have excellent antistatic properties but have bad influences on the photographic characteristics of photographic materials, such as sensitivity, fog properties, graininess or sharpness of photographic emulsions, or they stain processing solutions for development or cause adhesion of insoluble substances onto rollers during development. Accordingly, it has been extremely difficult to apply these substances to photographic materials.
The antistatic technique using nonionic surfactants is closely related to the coating aids used together with surfactants. These surfactants may be effective for improving the antistatic property of photographic materials, but in the use of the surfactants no consideration is taken on the probability of staining of processing solutions or conveyor rollers in development, which causes severe accidents in films processed.
For example, Japanese Patent Publication No. 9610/76 (corresponding to U.S. Pat. No. 3,850,641) discloses that phenol-formalin condensation product/ethylene oxide addition-polymers are effective as an antistatic agent when used together with various coating aids. However, the method of the publication does not solve the problems caused by staining during development step.
Specifically, the conveyor roller stain which is considered to be caused by the dry deposit formed on the rollers is extremely severe and causes a significant problem of density unevenness of films.
Japanese Patent Application (OPI) No. 29715/78 (corresponding to British Patent No. 1548799) discloses photographic light-sensitive materials which contain particular anionic surfactants and polyoxyethylene series nonionic surfactants. However, even by the use of the combined surfactants, the film damage caused by staining or processing solutions or conveyor roller in development process could not be solved.
Recently, a method of reducing the amount of water used for development processing for the purpose of preventing environmental pollution, economizing water resources, reducing manufacturing costs and simplifying processing apparatus, etc., has been developed, along with a method of reducing the amount of replenishers to be used for the purpose of reducing manufacturing costs and a method of increasing the concentration of processing solutions for the purpose of shortening the processing time. Under these situations, the staining of processing solutions and the deposition of water-insoluble substances onto conveyor rollers are becoming more and more noticeable, and are significant problems in the recent photographic processing field.